The present invention relates to an apparatus for diagnosing a plurality of digital-to-analog converters simultaneously.
Various kinds of electronic instruments employ digital-to-analog converters (hereinafter referred to as DACs) for converting digital signals to analog signals. For example, the DAC generates a threshold voltage for an input logic signal in a logic analyzer controlled by a microprocessor. It is necessary to diagnose many functions of the electronic instrument for insuring the operation thereof, and one such operation requiring diagnosis is the DAC's operation.
A conventional diagnostic apparatus for DACs includes an analog-to-digital converter and a digital comparator. The output analog signal from the DAC is reproduced as a digital signal by the analog-to-digital converter, and the reproduced digital signal is compared with the input digital signal of the DAC by the digital comparator. However, this conventional diagnostic apparatus requires an expensive analog-to-digital converter. If a plurality of DACs must be diagnosed simultaneously, the diagnostic apparatus becomes more expensive because each DAC needs a set of the analog-to-digital converter and digital comparator. In addition, it requires a long time to diagnose a plurality of DACs in sequence by using a single analog-to-digital converter and digital comparator set.